Study on the Preparation and Protective Performance of Epoxy Resin-Modified Polyurethane and Polyurea Composite Coatings

To address the issues of traditional protective coatings that limited material diversity and protective performance are difficult to take into account， single-component polyol-based polyurethane molecular structures exist defects， and curing rate of polyurea is fast， by changing the mixing ratio of PTMG2000 and polyether 3050 in the polyurethane synthesis raw materials to regulate the degree of polyurethane crosslinking and microphase separation to improve its performance， and at the same time， P1000 and chain extender MDBA were used to prepare a slow-reaction polyurea that could be coated by hand， and epoxy resin was used as a primer and polyurethane-polyurea as a topcoat， to prepare a coating that has excellent wear-resistant， corrosion-resistant and impact-resistant protective properties.Results showed that when the ratio of m(PTMG2000) to m(polyether 3050) was 1 ∶2， the polyurethane prepared exhibited a tensile strength of 13.19 MPa， which represented an increase of 85.25%compared to PU-3050.The elongation at break was 289.14%， marking a 140%improvement.The temperature at which 50%thermal decomposition occurred increased from 392.45 ℃to 400.28 ℃， and the water contact angle increased from 90.72° to 98.29°，demonstrating overall performance enhanced.After 15 d of neutral salt spray testing，the composite coating showed no blistering and had a small corrosion area， exceeding the ISO 9227-2006 standard requirements.The adhesion was rated at level 0， surpassing the ISO 2409-2007 standard requirement of level 3.The impact resistance was 100 cm， exceeding the maximum 50 cm impact strength specified by the GB/T 1732-2020 standard.After 9 d of corrosion in a 3.5%NaCl solution， the impedance remained at 4.245×107 Ω·cm2， and the wear loss after 30 min was 10.28 mg， indicating excellent protective performance.